Process for the manufacture of artificial silks



Oct. 30, 1934. J DELPECH ET AL 1,978,741

PROCESS FOR THE MANUFACTURE OF ARTIFICIAL SILKS Filed June 29, 1931Patented Oct. 30, 1934 UNITED STATES PROCESS FOR THE MANUFACTURE OFARTIFICIAL SILKS Jacques Delpech and Constantin Heinrich, Amiens, FranceApplication June 29, 1931, Serial No. 547,740 In France July 5, 1930 1Claim.

The present invention has for its object a process for the manufactureof artificial silks with very fine unitary threads obtained fromsolutions of nitrocellulose in pure methyl alcohol, that is to saywithout the addition of other solvents. Either synthetic methyl alcoholor the one resulting from the pyrogeneous distillation of wood may bedifferently used.

According to the invention, the nitrocellulose is previously dehydratedby extraction of the water either by means or ethyl alcohol at about 95,or by means of methyl alcohol which is a little more diluted, between 80and 85 for example.

The said dehydrating operation is effected in a hydro-extractoraccording to the usual process.

After the water has been extracted, the nitrocellulose may still containabout 30% of methyl alcohol at 80, that is to say about 6% of water; thesaid nitrocellulose may be dissolved in pure methyl alcohol in theproportion of about 12 kg. of dry nitrocellulose, per 100 liters ofmethyl alcohol; the dissolution takes place very well without requiringthe addition of ethyl alcohol or of ether and the collodion which isobtained is in a perfeet condition for spinning.

The collodion which is thus obtained is spun or threaded by means ofpumps and dies with multiple holes, made of silver, nickel or any otherlittle oxidizable metal in an aqueous solution of 9 methyl alcohol at atemperature which is not lower than 25, C., the concentration in alcoholof the coagulating bath being able to attain between 10 and 80%.

In order to prevent the unitary threads from sticking to one another, itis necessary to add to the bath of coagulation either soap at aconcentration ranging between 0.5 and 3% for example, or an emulsion ofvegetable oils in soap or an emulsion of animal or mineral oils orwaxes. It is thus possible to prevent the threads from adhering to oneanother, or from agglomerating, by treating the silk, while the same iswound, with the same bath of coagulation to which the same productsareadded.

The rate of expansion for silk having from 1 denier to 0.7 denier perthread may be comprised between 35 and 50 meters per minute.

Collodion made with pure methyl alcohol and dried nitrocellulose may bespun in the same way.

An essential point is that the silks obtained must be, beforedenitration, perfectly dried so as to allow a complete retraction; theoperation may be performed in a tunnel drier, the silks in skeins orspools being watered before they come out so that they can be handledand transported without danger. Another process consists in drying thesilk whilst the same is still on spools, in a vacuum drier, the spoolsor bobbins being mounted tubes through which a stream of tepid water ispassing; in the vacuum of the apparatus, be it only a partial one, thenitrocellulose cannot burn and, if the apparatus is filled with waterbefore the removal of the spools or bobbins, one has nothing to handlebut spools loaded with wet nitrocellulose, that is to say a quiteuninfiammable one.

This process of manufacture has the advantage of allowing to easilyrecover the methyl alcohol which is used.

The greatest part of the alcohol is first fixed in the bath ofcoagulation itself which constantly enriches itself in alcohol, whencethe necessity of diluting it through a constant admission of water.

The removed bath is then submitted to a simple distillation which allowsto recover the alcohol.

A form of construction of the plant which can be utilized for carryingout the process according to the invention is represented by way ofexample in vertical section in the accompanying drawing:

1 is aivat containing the bath of coagulation and enclosed within aglazed or metallic funnel 2, a wall 3 of which is cooled by thecirculation of a cooling fiuid or any other means, in order tocondensate a part of the alcohol vapours evolving from the bath. Thealcohol which is condensated in this manner trickles down along the saidwall and is collected by means of a gutter 4. A pipe 5 discharging intothe funnel, preferably below the said gutter, is connected to anaspirator (not shown) producing a slight vacuum and supplying arecovering apparatus with the excess of methylic vapours which have notbeen condensed on the cold wall 3.

The collodion to be spun is admitted through a pipe 6 into a pump 7which drives the same through a pipe 8 and a strainer 9 into a die 10disposed in the bath. The filaments 11 leaving the said die andcoagulated under the action of the bath are gathered into a thread 12which is guided by a thread-guide and winds itself upon spools 13carried by a support 14. The driving means for these spools which makesno part of this invention has not been represented.

The alcohol with which the thread wound upon the spools is impregnated,is recovered separately when the said spools have been carried to thedrying apparatus acting under vacuum.

We claim:

A process for the manufacture of artificial silks with very fine unitarythreads, consisting in dissolving the nitrocellulose containing about 6%of water in pure methyl alcohol and in spinning the solution thusobtained through an aqueous solution of methyl alcohol with the additionof a lubricant capable of preventing the spun threads to adhere to oneanother.

JACQUES DELPECI-I. CONSTANTIN HEINRICH.

